Rsbeck, I have been through exactly what you are experiencing. Krell amps are neutral, accurate, powerful, and painfully revealing. This is great when the source and the rest of the system are up to the task, but otherwise they can drive you crazy. I have the MC version of the FPB 350's and love them. However, it has taken some time and money to get the rest of the system up to par and I still need a first class cdp. I once had B&W N802's connected with junk speaker wire and it sounded horrible at medium to high listening levels. There was no bass and the highs would peirce your ears. I added Cardas GR speaker cables and that made a huge difference in bass extention and mellowed out the highs significantly. But I was still not satisfied. At the time, I was using the Krell HTS 7.1 as the pre with a old Denon cdp connected with a digital coax. I began to realize that the AV preamp was not going to give me the first class 2 channel performance that I was seeking. So, I sold that and the N802's. The N802's were purchased as a temp until I could find the speakers that I really wanted. I recently added a Krell KCT preamp and Wilson WP 7 speakers and now things are starting to gel. The resolution is unreal and the sound is smooth, powerful, full and sweet but I can hear the old Denon cdp in the chain. I am currently shopping for a cdp but have not made a decision yet.
I am not suggesting that you need to go through the changes and expense that I have. Your goals may be totally different than mine. But, if you are ever to be happy with Krell amps in your system, the rest of the system must be on par. They will definately let you know if something else in the chain is noisy. They are extremely revealing.
